1. Field of the Invention
The present invention relates to an apparatus and a method for reproducing information from an optical information recording medium using holography.
2. Description of the Related Art
Recently, standard of Blu-ray Disc using blue-violet semiconductor laser has realized commercialization of optical disc with recording density of approximately 50 GB in the consumer market.
The optical disc is highly demanded to have capacity as large as that of the HDD (Hard Disc Drive) with size ranging from 100 GB to 1 TB.
However, new type density growth technology different from the one using short wavelength and objective lens with large NA is required for the purpose of realizing the superdense optical disc.
There has been a trend to study storage technology for next generation, and the holographic recording technology for recording digital information with holography has been focused.
Japanese Unexamined Patent Publication No. 2004-272268 (Patent Document 1) discloses the hologram recording technology. The document discloses an angular multiplexing recording method for recording the hologram by interfering radiated reference beams of parallel light flux simultaneously with condensing the signal light flux on the optical information recording medium using lens, and performing multiplex recording by displaying different page data on the spatial light modulator while changing the incident angle of the reference beam to the optical recording medium. In the document, the signal beam is condensed by the lens, and the opening (spatial filter) is arranged in the beam waist so as to reduce the distance between adjacent holograms. This makes it possible to increase recording density/capacity compared with the related art angular multiplexing recording method.